Barriers for restricting the passage of vehicles (such as automobiles, trucks, busses, airplanes and the like) are generally known. Barriers that are fixed in the roadway, meaning they do not move by device or mechanism, are typically categorized as “passive” or “inoperable” barriers. These types of barriers are either removably placed on the roadway or sidewalk surrounding an at-risk site, or they are installed into the ground or built into the landscape/streetscape. Known installed “passive” barriers typically include foundation walls (typically at least 36″ high), or bollards in the form of “posts” embedded in a concrete foundation, and beds of a crushable material (such as concrete). Walls and bollards are intended to stop vehicles through impact resistance, having sufficient shear strength to remain intact at impact and relying on the inertia of their foundations to bring a vehicle to a halt.
In addition to vehicle barrier systems, vehicle arresting systems are also known. Where vehicle barrier systems are intended to immediately stop a vehicle, vehicle arresting systems are intended to control the stopping of a vehicle over a given time and/or distance. Known arresting systems include beds of a crushable material (such as concrete), fences and gates, and cable and elastic (e.g. “bungee cord”) systems. Crushable beds tend to utilize the interaction between the bed and the tire(s) of the vehicle. As a vehicle moves across the crushable material, the weight of the vehicle causes it to sink into the bed. At the same time, the spinning of the tire “rips” through the crushable material. As the vehicle drops farther into the bed, the tires' rotation tends to become slower until finally the vehicle is stopped. For example, crushable beds at the ends of aircraft runways for aircraft that “overshoot” the runway are generally known for gradually decelerating the aircraft over an extended distance to minimize injury to occupants and damage to the aircraft. Examples of such crushable bed systems are described in U.S. Pat. Nos. 5,885,025; 5,902,068 and 6,726,400.
These known vehicle barriers present a number of functional problems. Walls significantly impede pedestrian traffic and can cause pedestrian “herding” and “bottle necking.” Additionally, walls, and bollards as well, are somewhat visually restricting. The inherent height of the two, that is necessary for their function as a vehicle barrier, reduces the visual “openness” of the landscape/streetscape. Crushable beds are not optimal because they typically require an extended length of the crushable bed (upwards of 50 feet or more) to arrest a vehicle (and substantially longer for aircraft and the like). Such long lengths are generally not compatible with most urban applications, where space between a roadway and a building line or perimeter line is fairly small (e.g. 5–30 feet) and a primary objective of the barrier is to stop the progress of the vehicle within a relatively short distance. Such known vehicle barrier systems tend to provide limited application and flexibility to designers in providing an effective vehicle barrier system intended to meet applicable government performance standards, and is minimally obtrusive, for use in areas such as urban settings that typically have limited space for installation of such barriers.
Accordingly, it would be desirable to provide an installed vehicle barrier system or the like of a type disclosed in the present Application that include any one or more of these or other advantageous features:                1. A system providing a barrier that is resistant to unauthorized breach by vehicles.        2. A system that minimizes the restriction of pedestrian traffic flow.        3. A system that provides a less visually obtrusive installed vehicle barrier system.        4. A system that stops a vehicle in the short distance between a roadway and the protected site.        5. A system that rapidly arrests a vehicle without regard to vehicle damage.        6. A system that is integrated into the landscape/streetscape, employing similar elements such as curbs, sidewalks, benches, etc.        7. A system that combines a trafficable roadway surface, a curb, a bed of compressible material covered by a surface cover layer, and a low wall line or low bollard line.        8. A system in which the required height of the impact element line is interdependent with the characteristics of the bed of compressible material, so that the various components of the system may be adjusted to suit the needs of a particular application.        